JP2009530140A - Manufacturing method of shaped part and shaped part obtained by said method - Google Patents

Abstract

The present invention
-Stacking two or more sheets comprising a single layer of unidirectional impact resistant fibers and binder to form a stack; then placing the stack in a mold; and stacking the mold in the mold Fixing with the control member, closing the mold,
-Solidifying the stack under temperature and pressure to form a curved shaped part. The invention further relates to the product obtained by said method, which product is very suitable for use in impact resistant applications, such as helmets, curved panels, conical signs and domes.
[Selection figure] None

Description

Detailed Description of the Invention

  The present invention relates to a method for manufacturing a shaped part and a shaped part obtained by the method. The shaped parts obtained by the method are very suitable for use in impact resistant applications, such as helmets, curved panels, conical signs and domes.

  A method for manufacturing shaped parts is known from US Pat. No. 4,613,535. This publication discloses the production of shaped parts by stacking sheets comprising a single layer with impact resistant fibers onto a rigid layer and then compressing. In this sheet, impact resistant fibers are embedded in a thermoplastic matrix, which has an elastic modulus of less than 41 MPa. Example 2 of U.S. Pat. No. 4,613,535 applies a general epoxy resin to two 2 × 2 basket woven Kevlar (Kevlar®) 29 fabrics, and then between Apollo plates It is disclosed that a cured rigid layer is produced by curing at 105 ° C. and a pressure of 0.41 MPa for 90 minutes. On this cured rigid layer, a single layer of unidirectional high performance polyethylene (HPPE) fiber is placed in a polystyrene-polyisoprene-polystyrene matrix such that the fiber direction of each single layer is perpendicular to the fiber direction of the adjacent layer. The containing sheets were stacked and then pressed between the two platens in a hydraulic press at approximately 0.55 MPa and 130 ° C. and subsequently cooled to 50 ° C. under pressure.

  A disadvantage of the method according to US Pat. No. 4,613,535 is that, for example, when a curved shaped part such as a helmet is manufactured, its impact performance varies depending on the position on the curved shaped part.

  An object of the present invention is to provide a method for manufacturing a shaped part in which the impact performance of the shaped part is unlikely to vary depending on the position on the curved shaped part.

This purpose is
-Stacking two or more sheets comprising a single layer of unidirectional impact resistant fibers and binder to form a stack, wherein the direction of fibers in a single layer is relative to the fiber direction of an adjacent layer Step that is at an angle of α, and then
-Putting the stack into the mold;
-Fixing the stack in the mold with a control member;
-Closing the mold;
The solidification of the stack under temperature and pressure into a curved shaped part, after which the step of removing the shaped part from the mold is achieved.

  In the method according to the invention, the shaped part to be produced is a shaped part whose impact performance change between positions on the curved shaped part is produced by the method according to US Pat. No. 4,613,535. Less than. The curved shaped part in this application means a part having a double curvature, that is, a part bent along two mutually perpendicular axes (that is, deviating from a plane).

  An additional advantage of the method according to the invention is that the shaped part is manufactured in one step, which makes it more efficient than the known method.

  In the method according to the invention, the term single layer of unidirectional impact resistant fibers refers to a layer of a unidirectionally oriented impact resistant fiber network and a binder (essentially connecting the fibers). The term unidirectionally oriented fibers refers to fibers on one plane that are oriented substantially parallel.

  The term fiber includes not only monofilaments but, inter alia, multifilament yarns or flat tapes. The width of the flat tape is preferably between 2 mm and 100 mm, more preferably between 5 mm and 60 mm, and most preferably between 10 mm and 40 mm. The thickness of the flat tape is preferably between 10 μm and 200 μm, more preferably between 25 μm and 100 μm.

  The impact resistant fibers in the single layer of the present invention have a tensile strength of at least about 1.2 GPa and a tensile modulus of at least 40 GPa. These fibers may be inorganic fibers or organic fibers. Suitable inorganic fibers are, for example, glass fibers, carbon fibers and ceramic fibers. The inorganic fiber is preferably a carbon fiber produced from polyacrylonitrile.

  Suitable organic fibers having such a high tensile strength are, for example, liquid crystalline properties such as aromatic polyamide fibers (so-called aramid fibers) (especially poly (p-phenylene terephthalamide)), polybenzimidazoles or polybenzoxazoles. Polymer fibers and ladder-like polymer fibers (especially poly (1,4-phenylene-2,6-benzobisoxazole) (PBO), or poly (2,6-diimidazo [4,5-b-4 ', 5'-e] pyridinylene-1,4- (2,5-dihydroxy) phenylene) (PIPD; also referred to as M5)) and highly oriented fibers such as polyolefins, polyvinyl alcohol, and Polyacrylonitrile fiber, for example, by gel spinning method Those obtained Te, and the like. The fibers preferably have a tensile strength of at least 2 GPa, more preferably at least 2.5 GPa or most preferably at least 3 GPa. The advantage of these fibers is that they have a very high tensile strength, so that they are very suitable for use in particularly lightweight and impact-resistant articles.

  Suitable polyolefins are in particular ethylene and propylene homopolymers and copolymers, which may also contain small amounts of one or more other polymers, especially other alkene-1-polymers.

Good results are obtained when linear polyethylene (PE) is selected as the polyolefin. As used herein, linear polyethylene is understood to mean polyethylene having less than one side chain per 100 C atoms, preferably polyethylene having less than one side chain per 300 C atoms, The branch generally has at least 10 C atoms. The linear polyethylene may further contain up to 5 mol% of one or more other alkenes (propene, butene, pentene, 4-methylpentene, octene, etc.) copolymerizable therewith. The linear polyethylene is preferably of a large molar mass with an intrinsic viscosity (IV, measured with decalin solution at 135 ° C.) of at least 4 dl / g, more preferably at least 8 dl / g. Such polyethylene is also referred to as ultra high molar mass polyethylene. Intrinsic viscosity is a measure of molecular weight that can be more easily measured than actual molar mass parameters such as _Mn and _Mw . There are several empirical relationships between IV and _Mw , but such relationships are highly dependent on molecular weight distribution. Based on the formula M _w = 5.37 × 10 ⁴ [IV] ^1.37 (see EP 0504951 A1), 4 or 8 dl / g of IV is equal to about 360 or 930 kg / mol of M _w , respectively. Let's go.

  High performance polyethylene (HPPE) fibers composed of polyethylene filaments prepared by gel spinning methods (such as those described in GB 2042414 A or WO 01/73173) are preferably used as impact resistant fibers. . In that case, very good impact / weight performance is provided. The gel spinning method basically consists of preparing a solution of linear polyethylene having a high intrinsic viscosity, making a filament from the solution at a temperature above the melting temperature, and cooling the filament to a temperature below the gelation temperature to form a gel. And stretching the filament during or after removal of the solvent.

  The term “binder” refers to a material that bonds or joins fibers in a sheet that includes a single layer of unidirectionally oriented fibers and binder, where the binder is a single layer structure when handling or making a preformed sheet. So that all or part of the fiber can be surrounded. The binder can be applied in various forms or ways. For example, as a film (by melting it and at least partially covering the impact resistant fibers), as a cross-bonding strip or transverse fibers (transverse to unidirectional fibers), or a matrix material (eg, polymer melt, The solution can be applied by impregnating the fiber with a solution or dispersion containing a polymer material in a liquid and / or embedding the fiber with a matrix material. The matrix material preferably extends evenly over the surface of the single layer, but the bonding strips or fibers may be applied locally. Suitable binders are described, for example, in EP 0191306 B1, EP 1170925 A1, EP 0683374 B1 and EP 1144740 A1.

  In a preferred embodiment, the binder is a polymer matrix material and may be a thermosetting material or a thermoplastic material, or a mixture of the two. The elongation at break of the matrix material is preferably greater than the elongation of the fibers. The binder preferably has an elongation of 2 to 600%, more preferably an elongation of 4 to 500%. Suitable thermosetting and thermoplastic matrix materials are listed, for example, in WO 91/12136 A1 (pages 15 to 21). When the matrix material is a thermosetting polymer, vinyl esters, unsaturated polyesters, epoxy resins or phenol resins are preferably selected as the matrix material. Where the matrix material is a thermoplastic polymer, preferably a polyurethane, polyvinyl, polyacryl, polyolefin or thermoplastic elastomer block copolymer (such as polyisopropene-polyethylene-butylene-polystyrene or polystyrene-polyisoprene-polystyrene block copolymer) is the matrix. Selected as material. The binder is preferably composed of a thermoplastic polymer, which preferably completely covers the individual filaments of the fibers in a single layer, the binder being measured according to (ASTM D638 (25 ° C.) The tensile modulus is at least 75 MPa, more preferably at least 150 MPa, even more preferably at least 250 MPa, and most preferably at least 400 MPa. The binder preferably has a tensile modulus of 1000 MPa or less. Such a binder makes the sheet containing the single layer more flexible and provides a sufficiently high stiffness in the solidified stack. When the impact resistant fiber is an inorganic fiber, the binder preferably has a tensile modulus (measured according to ASTM D638 (25 ° C.)) of at least 500 MPa, more preferably at least 750 MPa. If a very hard sheet comprising a single layer is required, the tensile modulus is preferably at least 1500 MPa.

  The amount of the binder in the single layer is preferably 30% by mass or less, more preferably 25% by mass or less, 20% by mass or less, or indeed 15% by mass or less. This provides the best impact performance.

  In the method according to the invention, the stack is formed by stacking two or more sheets comprising a single layer of unidirectional impact resistant fibers and a binder, in which case the single layer of fiber direction is adjacent. An angle of α with respect to the fiber direction of the layer, and in that case α is preferably between 5 and 90 °, more preferably between 45 and 90 °, most preferably between 75 and 90 °. .

  The resulting stack is typically placed in an open mold (generally comprised of a female part and a male part), after which the stack is secured to one part of the mold (typically a female part). The This fixing is performed by a so-called control member. Also, the stack is mounted in place with respect to the female mold part so that the stack can still slide when the mold is closed (ie when the male part is moved into the female mold part). This fixing is done. This fixing by the control member can preferably be done by pressing the stack against the female mold part from the outer area. The fixing force of the control member on one part of the mold is preferably in the range between 50 and 5000 N, more preferably between 100 and 3000 N, and should be optimized by some routine experimentation by those skilled in the art. Can do. During optimization, those skilled in the art will select a clamping force that is large enough to press the stack into the female mold part, along with this fixing force when closing the mold. It is small enough that the stack can slide into the female mold part.

  After fixing the stack to one part of the mold, for example, the male part is moved into the female mold part to close the mold, thereby pressing the stack to stabilize the shape of the mold. Thereafter, the stack is solidified under temperature and pressure into a shaped part, that is, a curved shaped part. If the matrix material is a thermoplastic polymer, solidification is accomplished by cooling the stack after melting the thermoplastic polymer. If the matrix material is a thermosetting polymer, solidification is performed by heating and reacting the thermosetting polymer, after which the stack is cooled.

  The temperature during solidification is generally controlled by the mold temperature. The temperature during melting or reaction is generally selected from below the temperature at which the impact resistant fiber loses its high mechanical properties (eg, due to melting). The mold temperature is preferably at least 10 ° C., preferably at least 15 ° C., more preferably at least 20 ° C. lower than the melting temperature of the fibers. If the fiber does not exhibit a clear melting temperature, the temperature at which the fiber begins to lose its mechanical properties should be read instead of the melting temperature. The temperature at which the fiber begins to lose its mechanical properties is referred to in this application as the softening temperature. For example, for HPPE fibers that often have a melting temperature of 155 ° C., a mold temperature of generally less than 135 ° C. will be selected. The minimum temperature is generally selected to provide a reasonable solidification rate. In this regard, 50 ° C. is a suitable lower temperature limit, which is preferably at least 75 ° C., more preferably at least 95 ° C., and most preferably at least 115 ° C.

  The pressure during solidification is preferably at least 7 MPa, more preferably at least 10 MPa, even more preferably at least 13 MPa, and most preferably at least 16 MPa. By such a method, the impact resistance performance is further improved. Optionally, a low pressure pre-shaping step may be performed prior to this solidification. The pressure during this pre-forming step may vary from 2 to 5 MPa. After pre-molding and before solidification, the mold can be opened to check for blisters, which can then be removed, for example, with a sharp object. Other options to prevent blistering include venting or vacuuming during molding.

  The optimum time for solidification depends on conditions such as temperature, pressure, and part thickness, but is generally in the range of 5 to 120 minutes, and can be confirmed by ordinary experiments.

  If the matrix material is a thermoplastic polymer, the stack is allowed to cool and solidify. Cooling is preferably performed while maintaining the pressure. If it does so, impact resistance performance will become high. Cooling is performed until the shaped part reaches a temperature of 90 ° C. or lower, preferably 75 ° C. or lower, more preferably 50 ° C. or lower. As soon as the shaped part reaches this temperature, the mold can be opened and the shaped part is removed from the mold. Any possible waste is later cut from the shaped part. In addition, the shaped part may be further processed to the desired final dimensions by known mechanical techniques such as sawing, polishing, drilling and the like.

  In a preferred embodiment of the method according to the invention, the two or more sheets comprising a single layer of unidirectional impact-resistant fibers and binder are rectangular sheets, more preferably square sheets, The direction of the impact resistant fiber is parallel to the diagonal of the sheet. As a result, the least amount of debris is removed from the solidified product. Reducing the amount of litter is an important issue, especially for high performance impact resistant fibers such as HPPE and aramid. This is particularly advantageous in terms of the high cost of these fibers.

  Upon formation of the stack in the method according to the present invention, optionally, at least one layer of the second impact-resistant fiber fabric comprises two or more sheets comprising a single layer of unidirectional impact-resistant fibers and binder. It may be placed on or between the sheets. Whenever the stack is formed, this layer of fabric of the second impact resistant fiber may be at any location throughout the stack, but this layer of fabric will have this fabric on the impact surface of the shaped part obtained in this way. It is preferably arranged in the stack in a close-up manner. In a special embodiment, the fabric can also form the very impact surface of a curved shaped part obtained with the method according to the invention. The impact surface of a shaped part is the side of the product that encounters a ballistic impact. The fabric layer may comprise a binder selected from the polymers listed above.

  The second impact resistant fiber may be selected from the range of impact resistant fibers listed above. In a particular embodiment of the method according to the invention, the unidirectional impact fiber and the second impact fiber in the fabric layer are based on the same type of polymer. Thereby, in the shaped part, the possibility of delamination between the stack and the fabric is lowest. The impact resistant fibers are most preferably based on polyethylene fibers, preferably obtained by the gel spinning method described above.

  In the method of the present invention, the unidirectional impact resistant fiber is preferably an organic fiber, and the second impact resistant fiber is preferably an inorganic fiber.

  In a preferred embodiment of the method according to the invention, the impact-resistant fibers or the second impact-resistant fibers in at least one of the layers very close to the impact surface are embedded in a thermosetting matrix. In this way, a harder shaped part can be obtained. This thermosetting matrix is selected from the group of thermosetting polymers already listed above.

  In yet another preferred embodiment of the method according to the invention, the part of the rectangular or square sheet in the stack is a sheet with a smaller surface area, preferably a circular sheet (for example an oval or circular sheet). Etc.). In this case, the ratio of the surface area of such a circular sheet to such a rectangular or square sheet should be in the range of 2 to 75% by weight, preferably 5 to 60%, more preferably 10 to 40%. (Percentage in this application is percent by weight unless otherwise specified). The fiber direction of the oval or circular sheet is selected to be at an angle α with respect to the fiber direction of the adjacent single layer, where α is between 5 and 90 °. The ratio between the number of round sheets and the number of rectangular or square sheets may be in the range of 2-20%, preferably 4-10%. This improves the surface properties of the curved shaped part. Preferably, at least one or more rectangular or square sheets are alternated with at least one oval or circular sheet. In the case of helmets often referred to as “crowns”, it is preferable to place at least one oval or circular sheet closest to the impact surface. This is because a sheet comprising a single layer of unidirectional impact resistant fibers disposed between at least one oval or circular sheet and the impact surface is between the oval or circular sheet and the opposite surface of the impact surface. It means less than a sheet containing a single layer of unidirectional impact resistant fibers. In general, rectangular or square sheets and oval or circular sheets are stacked such that their centers are on top of each other. The oval or circular sheets are preferably placed on top of each other so that there are no other layers between them. In order to improve the surface properties of the resulting curved shaped part, it is preferred that the diameters of the oval or circular sheets are different.

  In another preferred embodiment of the method according to the invention, it comprises a single layer of unidirectional impact resistant fibers and a binder, the direction of each single layer of impact resistant fibers being an angle α with respect to the fiber direction of the adjacent single layer. And the stack of two or more sheets further comprises at least one carbon fiber sheet. The carbon fiber sheet is a sheet comprising woven or non-woven carbon fibers (including unidirectional orientation) and preferably a binder, wherein the binder is selected from the ranges listed above. The carbon fiber sheet is preferably composed of carbon fibers and a binder. The surface area of the carbon fiber sheet may be the same as the surface area of the sheet comprising a single layer of unidirectional impact resistant fibers and binder.

  The surface area of the carbon fiber sheet is preferably 80% or less of the surface area of the sheet including a single layer of unidirectional impact resistant fibers and a binder, more preferably the surface area of the carbon fiber sheet is 60% or less, Even more preferably, the surface area of the carbon fiber sheet is 30% or less of the surface area of the sheet comprising a single layer of unidirectional impact resistant fibers and a binder.

  The surface region of the carbon fiber sheet may be configured to cover the center of the sheet including a single layer. Such a surface may be in the form of a closed circle. The advantage is that the shaped part (for example in the form of a helmet) obtained with the method according to the invention provides further protection against collisions from above, for example due to falling rocks. This carbon fiber sheet is preferably located in the stack close to the impact surface. We believe that such a carbon fiber sheet in a form that covers the central part of the shaped part (which has a smaller surface area than the final shaped part) is subject to impact (more specifically impact impact). It has further been found that it can be used very satisfactorily for any other shaped part that does not contain fibers. In this way, the stated advantage of improved protection against collisions from above is maintained.

  However, the surface region of the carbon fiber sheet may be in a form that does not cover the central portion of the sheet including a single layer. Such a surface may be in the form of an open circle or an annulus. The advantage is that the shaped part (for example, in the form of a helmet) obtained with the method according to the invention has a high lateral stiffness. This means that for those wearing such a helmet, for example, the side protection of the ears during a collision is further improved. This carbon fiber sheet is preferably in a position in the stack close to the stack surface opposite to the impact surface. The inventors have determined that such a carbon fiber sheet in a form that does not cover the central part of the shaped part (ie, a carbon fiber sheet having a cut-out, preferably a central cut-out) is subjected to a collision (more specifically, It has further been found that it can be used very well for any other shaped part that does not contain unidirectional fibers (which undergo impact collisions). In this way, the stated advantage of improved side protection is maintained.

  Therefore, the carbon fiber sheet is particularly suitable for use in the production of curved shaped parts including organic impact resistant fibers. Such organic impact resistant fibers are preferably the gel-spun polyethylene or aramid fibers. Depending on the requirements of a particular application of such a shaped part, both of the aforementioned surface areas of the carbon fiber sheet can be combined in one shaped part.

  In yet another preferred embodiment of the method according to the invention, there is a cutout in the central part of the stack of sheets comprising a single layer of unidirectional impact-resistant fibers and binder, and optionally at least one fabric layer , For example, in a form in which the circular area of the layer is cut out leaving an open space in the center. In general, such circular areas will have a surface area of less than 60%, preferably less than 40% of the surface area of a single layer. The advantage is that, for example, a curved shaped part in the form of a top-opening helmet that is convenient for the tropical region can be manufactured. Alternatively, the central open space may be cut out from the solidified shaped part.

  Instead of a single layer stack of unidirectional impact resistant fibers, the method according to the invention can be carried out in a similarly convenient manner with a stack of fabrics. However, such a method is most preferred because the method according to the present invention using a single layer of unidirectional impact resistant fibers results in a product with higher impact resistance.

  The method according to the invention results in a shaped part with less impact performance change between positions on the curved shaped part than the shaped part produced by the method according to US Pat. No. 4,613,535. . The invention therefore also relates to a curved shaped part obtained by the method according to the invention. An additional advantage of the curved shaped part according to the invention is that the Vo value at a given weight (i.e. the maximum speed of the bullet or debris that does not penetrate the part) is increased. Curved shaped parts obtained by the method according to the invention include, for example, helmets, helmet shells, curved panels, conical signs and domes.

  Thus, the present invention also includes two or more sheets, each sheet comprising a single layer of unidirectional impact resistant fibers and a binder, wherein each single layer of impact resistant fibers is in the direction of an adjacent single layer. The present invention relates to a curved shaped part including two or more sheets having an angle α with respect to the fiber direction and at least one carbon fiber sheet. The unidirectional impact resistant fiber is preferably the polyethylene fiber, more preferably HPPE; aramid fiber or ladder polymer fiber. More preferably, the unidirectional impact resistant fiber is the polyethylene fiber. In this case, for example, a curved shaped part that is as light as possible is produced while still providing good protection against shock hazards.

  The curved shaped part obtained by the method according to the invention is very suitable for use in the production of impact resistant articles.

[The test methods mentioned in this application are as follows]
IV: Intrinsic viscosity is measured according to the method of PTC-179 at 135 ° C. in decalin (Hercules Inc. review, April 29, 1982 (Rev. Apr. 29, 1982)), the dissolution time is 16 hours, DBPC is used as an antioxidant in an amount of 2 g / liter solution and the viscosity measured at various concentrations is extrapolated to zero concentration.

Side chains: The number of side chains in a UHPE sample is determined by FTIR with a compression molded film with a thickness of 2 mm, the absorption at 1375 cm ⁻¹ is measured, and a calibration curve based on NMR measurements is used (eg, EP As in 0269151).

Tensile properties (measured at 25 ° C.): Tensile strength (or strength), tensile modulus (or modulus) and elongation at break (or eab) are defined as specified in ASTM D885M, multifilament Measure with yarn. The nominal gauge distance of the fiber is 500 mm and the crosshead speed is 50% / min. The elastic modulus is determined as the slope between 0.3 and 1% strain based on the measured stress-strain curve. To calculate the modulus and strength, the measured tensile force is divided by the titer measured by weighing 10 meters of fiber and the value (in GPa) assumes a density of 0.97 g / cm ³ calculate. The tensile properties of the thin film were measured according to ISO 1184 (H).

  Impact resistance test procedure: Firing was performed using 1.1 grams of Fragment Simulating Projectiles (FSP). The launch was performed such that the intended FSP speed was approximately equal to the expected V50 (680 meters / second). The actual FSP speed was measured before the collision. If penetration occurred, the speed of the next launch was reduced by the expected amount of 15 m / s (note that it is impossible to set the FSP speed accurately in advance). With the amount of explosion and the way of loading, only the speed set value can be estimated. However, the velocity measurement before the collision is very accurate. When the projectile stopped, the next target FSP speed was increased by 15 m / sec. For each helmet, eight shots were made around the helmet edge at approximately the same distance from each other and approximately 6 cm from the helmet edge (thus eliminating the edge effect).

  The final V50 was determined as the average of the three highest speeds at which stop occurred and the three lowest speeds at which penetration occurred. The same number is used to calculate the standard deviation. Other launches were considered too far away from V50 to be relevant and therefore their results were ignored.

[Example 1]
A square shaped stack measuring 59 cm x 59 cm was made from 92 single-layered sheets containing unidirectionally aligned fibers and 8 single-layered circular sheets containing unidirectionally aligned fibers. Here, the fiber direction of each single layer forms an angle of 90 ° with respect to the adjacent single layer. A single layer stack consists of eight square sheets (59 ^* 59 cm) with unidirectionally aligned fibers, the direction of the impact fibers being parallel to the diagonal of the square sheet, counting from the subsequent impact surface. There were 8 circular sheets with a single layer and a circular surface area (diameter 30 cm) and 84 square sheets. The center of each circular sheet was placed on the center of the adjacent sheet. Each monolayer includes a gel spun polyethylene fiber having a strength of 35 cN / dtex and a 19 wt% polyurethane matrix, in which case the areal density of the monolayer is 63 g / m ² . The completed stack was placed in a controlled clamp mold in the form of a helmet, the mold including a female part, a male part and a control member. A fixed pressure of about 2000 N is applied to the control member so that the stack is mounted in place relative to the female mold part in a flat state, but so that the stack can continue to slide when the mold is closed. The mold was closed by lowering the male part of the mold into the female part, while the flat stack was slowly placed against the female mold surface. This closure was done slowly during a 5 minute period to allow temperature transfer from the male and female mold sections to the stack. The mold temperature was about 125-130 ° C. The applied pressure was 5 MPa, and the stack was held in the mold until the temperature at the center of the stack reached 120 ° C. The pressure was then increased to a compression pressure of about 20 MPa and the stack was kept under this pressure for 15 minutes. The stack was then cooled to a temperature of 60 ° C. with the same compression pressure. After that, the mold was opened and scraps were cut from the helmet to smooth the edges of the helmet.

The weight of the manufactured helmet was 7.4 kg / m ² in terms of areal density. The average thickness of the helmet was 10.5 mm and the circumference was 75 cm. The manufactured helmets are called helmet numbers 1 and 2.

[Comparative Experiment A]
A square shaped stack measuring 59 cm x 59 cm was made from 100 single layers containing unidirectionally aligned fibers. Here, the fiber direction of each single layer forms an angle of 90 ° with respect to the adjacent single layer. Each monolayer includes a gel spun polyethylene fiber having a strength of 35 cN / dtex and a 19 wt% polyurethane matrix, in which case the areal density of the monolayer is 63 g / m ² . The completed stack was placed on the female part of a standard mold in the shape of a helmet, the mold including a female part and a male part. The mold was closed by lowering the male part of the mold into the female part, whereupon the stack was slowly placed against the female mold surface. This closure was performed slowly during a 5 minute period to allow temperature transfer from the male and female mold sections to the stack. The mold temperature was about 125-130 ° C. The applied pressure was 5 MPa, and the stack was held in the mold until the temperature at the center of the stack reached 120 ° C. Thereafter, the pressure was increased to a compression pressure of about 20 MPa and the stack was kept under this pressure for 15 minutes. The stack was then cooled to a temperature of 60 ° C. with the same compression pressure. After that, the mold was opened and scraps were cut off from the helmet to smooth the edges of the helmet. The manufactured helmets are referred to as helmet numbers A and B.

[result]
Helmets according to the invention (numbers 1 and 2) were tested together with two conventional helmets (numbers A and B) made by the method according to the prior art.

  Helmets 1 and 2 had a small standard deviation because of little variation in material performance. Furthermore, helmets 1 and 2 have a large V50 and a large Vo value (that is, a fragment speed at which substantially no fragments have penetrated the helmet).

It is extremely important that the material of life-saving products (such as helmets) is as robust as possible. The risk of lethal injury increases due to the weak spots that tend to occur and the associated low penetration rate. Correspondingly, the maximum speed (Vo) at which the material functions effectively (ie, does not substantially penetrate) is a very important performance indicator. It is not statistically likely that the measurement of V ₀ is very complex and there is no risk of penetration. A practical approximation of V0 is the speed at which penetration occurs only at 1 / 100th of the projectile. This Vo is sufficiently estimated by the 3-σ rule (that is, V50-3 ^* standard deviation). In the helmets (Nos. 1 and 2) of the present invention, the collision speed at which failure (penetration) does not occur is increased, and the larger collision speed is tolerated. This excellent performance reflects the method of manufacturing the curved surface portion that has little structural change.

[Example 2]
A helmet (number “3”) was manufactured according to Example 1, except that this method was pressurized to 5 MPa by removing the male part and opening the mold immediately after the center of the stack reached 120 ° C. Was interrupted in between. The pre-compressed helmet remained in the female part of the mold. Five carbon fiber sheets having a width of about 10 cm were placed on the inner surface of the helmet, and the sides of the carbon fiber sheets were aligned with the edges of the helmet. Thus, a carbon fiber ring was placed in the helmet. The carbon fiber sheet includes unidirectionally aligned carbon fibers that have a total areal density of about 200 g / m2. Commercially available carbon fibers made from polyacrylonitrile were used. The carbon fiber sheet further contained 38% by weight binder based on a thermosetting epoxy resin system.

  The mold was closed again and pressurized at 5 MPa for 3 minutes so that the carbon fiber sheet was also at the mold temperature. Thereafter, following the procedure according to Example 1 again, the pressure is increased to a compression pressure of about 20 MPa, the stack is kept under this pressure for 15 minutes, and then the stated cooling is carried out to a temperature of 60 ° C. at the same compression pressure. went. The protection of the side of the helmet was measured with a side-displacement test. In this test, the helmet was placed in a tensile tester so that a certain force was applied to the side of the helmet. The position of the side where the force was applied was the part of the helmet that protected the wearer's ear, thereby causing the dent of the helmet. The results are shown in Table 2.

In the case of helmet 1, when a force of 500 N was applied, a lateral displacement (dent) of 120 millimeters occurred, but in helmet number 3, only a displacement of 10 millimeters was seen at 1100 N, which is a double force. This clearly shows the improved side protection of these helmets.

Claims (26)

A method for manufacturing a shaped part,
-Stacking two or more sheets comprising a single layer of unidirectional impact resistant fibers and binder to form a stack, wherein said stack comprises a single layer of unidirectional impact resistant fibers and binder; The direction of the impact-resistant fibers of the sheet is at an angle α with respect to the fiber direction of the adjacent single layer; and then-placing the stack in a mold;
-Fixing the stack in the mold with a control member;
-Closing the mold;
-Solidifying said stack under temperature and pressure to form a curved shaped part.   The method of claim 1, wherein the sheet comprising a single layer of unidirectional impact resistant fibers and a binder is a rectangular sheet, wherein the direction of the impact resistant fibers is parallel to a diagonal of the rectangular sheet. .   The method according to claim 1 or 2, wherein the binder is a thermoplastic matrix having a tensile modulus of at least 250 MPa.   4. At least one layer of impact-resistant fiber fabric is disposed on the two or more sheets comprising a single layer of unidirectional impact-resistant fibers and a binder when forming the stack. The method according to any one of the above.   5. A method according to any one of the preceding claims, wherein the impact resistant fibers in at least one of the layers very close to the impact surface are embedded in a thermosetting matrix.   The method according to claim 4 or 5, wherein the impact resistant fibers of the fabric layer are embedded in a thermosetting matrix.   7. A method according to any one of claims 2 to 6, wherein 5 to 60% by weight of the rectangular or square sheets in the stack of single layers is replaced with sheets of smaller surface area.   The method according to any one of claims 1 to 7, wherein the impact-resistant fiber is a polyethylene fiber.   9. A method according to any one of the preceding claims, wherein the control member fixes the stack in the mold with a fixing force between 50 and 5000N.   The method according to claim 1, wherein the control member fixes the stack in the mold with a fixing force between 100 and 3000 N.   The method according to claim 1, wherein solidifying the stack into a curved shaped part is performed at a pressure of at least 7 MPa.   The method according to claim 1, wherein solidifying the stack into a curved shaped part is performed at a pressure of at least 13 MPa.   The pre-forming step of pressing the stack at a pressure between 2 and 5 MPa is performed before solidifying the stack into a curved shaped part at a pressure of at least 7 MPa. The method described.   14. A method according to any one of the preceding claims, wherein solidifying the stack into a curved shaped part is performed at a mold temperature that is at least 10 [deg.] C lower than the melting or softening temperature of the fibers.   15. A method according to any one of the preceding claims, wherein the stack comprises at least one carbon fiber sheet.   The method of claim 15, wherein the carbon fiber sheet comprises a plurality of single layers of unidirectional carbon fibers and a binder, wherein the direction of the carbon fibers is an angle α with respect to the fiber direction of an adjacent single layer.   The method of claim 15, wherein the carbon sheet comprises woven carbon fibers.   18. A method according to any one of claims 15 to 17, wherein the carbon sheet is between 20% and 80% of the surface area of the stack.   The method of claim 18, wherein the carbon sheet forms an annulus within the mold.   A curved shaped part obtained by the method according to claim 1. The pointed curved surface portion has a surface density of 7.4 kg / m ² or less and achieves a V ₀ of at least 620 m / s when using 1.1 gram simulated fragment projectile (FSP). 20. Curved shaped part according to 20.   Use of at least one carbon fiber sheet in the manufacture of curved shaped parts containing organic impact resistant fibers.   Two or more sheets, each sheet comprising a single layer of unidirectional impact resistant fiber and binder, wherein the direction of the impact resistant fiber of each single layer is α relative to the fiber direction of an adjacent single layer A curved shaped part including two or more sheets having an angle of at least one and at least one carbon fiber sheet.   The curved shaped part according to claim 23, wherein the impact resistant fiber is a polyethylene fiber.   The curved shaped part according to claim 23, wherein the impact resistant fiber is an aramid fiber or a ladder-shaped polymer fiber.   The curved shaped part according to any one of claims 20, 21, 23, 24, or 25, wherein the part has a shape of a helmet.